There has conventionally been known a technology of an image forming apparatus in which a plurality of units are mounted for executing image forming processes on sheets. In this technology, a process unit is disposed as a first unit and a drum unit with a photosensitive drum is disposed as a second unit. The drum unit is mounted beforehand in the process unit and then mounted in the image forming apparatus.
The technology described above has a special detector for detecting whether the process unit is mounted in an apparatus main body or not. Because the process unit is previously mounted with the drum unit and then mounted in the apparatus main body, the process unit and the drum unit cannot be mounted separately in the apparatus main body. This places a limitation to the procedures of an assembly work and a maintenance work. When, on the other hand, the drum unit and the process unit can be mounted separately in the apparatus main body, the number of detectors equivalent to the number of units is required in order to detect whether the units are mounted or not.
The present disclosure was contrived in view of the problems described above, and an object thereof is to provide an image forming apparatus in which a plurality of units are mounted, wherein the number of detectors for detecting whether units to be mounted separately in the apparatus are mounted or not is reduced as much as possible.